The power of love is a great and effective force in relation to society; the best societies are those which are administered by the power of love: both the love of the leader and the ruler for the people, and the love and devotion of the people for the leader and ruler.
The feeling and love of the ruler is an important factor in the stability and longevity of a government, and until that factor exists the leader cannot, or finds it very difficult to, lead the society, train people to be law-abiding individuals, and even establish justice and egality in that society. But once he does so, people will be so lawfully minded that they will see the affection of their ruler and it is this affection which will attract them to obedience and dutifulness.
The Qur'an addresses the Prophet and says to him that he has a great power in his hands to influence people and to administer society
It is by some mercy of Allah that thou art gentle to them; hadst thou been harsh and hard of heart, they would have scattered from about thee. So pardon them, and pray forgiveness for them, and take counsel with them in the affair. (A1 `Imran, 3: 159)
Here it is made clear that the cause of the people's coming to the Prophet is the affection and love which he has bestowed on them. Then it orders him to forgive them and to ask for forgiveness for them and to consult with them. These are all among the effects of love and friendship, just as tolerance, patience and forbearance are also among the degrees of love and kindness.
By the sword of clemency he (Ali) redeemed so many throats
Of such a multitude from the sword.
The sword of clemency is sharper than the sword of iron;
Nay, it is more productive of victory than a hundred armies. 
The Qur'an also says:
Not equal are the good deed and the evil deed. Repel with that which is fairer and behold, he between whom and thee there is enmity shall be as if he were a loyal friend. (Fussilat, 41:34 )
Forgive, o son, that man can trap
By goodness and do savage deeds with fetters,
Chain the neck of the enemy with mercy,
Which noose no blade can cut.
In his firman to Malik al-Ashtar, when he appointed him to the governorship of Egypt, Amir al-mu'minin also explained how his behaviour with the people should be:
Awaken in your heart mercy for (your) subjects and love for them, and kindness towards them . . . So give them of your forgiveness and your pardon, just as you would like Allah to give you of his forgiveness and pardon. 
The heart of the ruler must be a focus of affection and love towards the nation; power and force are not enough. People can be driven like sheep by power and force, but their inner strengths cannot be awakened and put to use. Not only is power and force not sufficient; even justice, if it is lifelessly enforced, is not enough. Rather the ruler must love the people from his heart like a loving father, show his affection towards them and also have an attractive personality which fosters devotion, so that he may make use of their wills, their ambitions and their great human strengths in furthering his own divine aim.
. Rumi, bk.l
. Nahju 'l-balaghah, Letter no. 53